Research On The Microstructure And Performance Of TiAlN Film Based On Surface Nanocrystallized Substrate On Cemented Carbide

As a refractory composite material with high hardness and wear resistance,cemented carbide is widely used in metal cutting,mining and wear resistance parts.Cemented carbide is the most popular and common tool material with high productivity.The world is vigorously researching and developing hard coatings for cutting tools.These hard coatings have been shown to extend tool life by slowing the wear characteristics of cutting tools.In recent years,surface nanocrystallization technology can form gradient nanocrystalline layer on the surface of metal substrate,which provides substrate material with excellent comprehensive performance for coating preparation.In order to improve the processing efficiency and precision of the modern manufacturing industry,prolong the service life of the tool,and realize the comprehensive modification of the traditional tool,it is necessary to improve the mechanical properties and corrosion resistance of the cemented carbide substrate,and scientifically combine the charactertics of the tool substrate and the hard coating.In this paper,ultrasonic shot peening technology and ultrasonic surface rolling technology were used to nanocrystallization of WC-8Co cemented carbides,respectively,to obtain the alloy with gradient nanostructure surface.The microstructure,mechanical properties and corrosion behavior of WC-8Co cemented carbides in 3.5% Na Cl solution before and after surface nanocrystallization were studied.On this basis,TiAlN film was prepared on the cemented carbide substrate before and after surface nanocrystallization by multi-arc ion plating equipment.The microstructure and properties of TiAlN film on the surface of WC-8Co cemented carbide were studied.Research indicates:(1)After ultrasonic shot peening,the average particle size of the most surface layer of WC-8Co cemented carbide is 40 nm,which realizes the nanocrystallization.After ultrasonic shot peening,the roughness of the sample increases,and the hardness of the surface increases by about 15.8% compared with that of the matrix.The hardness of the cross section changes in a gradient from the surface to the center.The corrosion current density of the electrochemical polarization curve is small after the nanocrystallization,which indicates that the corrosion resistance of the sample is improved after the nanocrystallization.The arc radius of the impedance spectrum of the original sample is smaller than that of the nanocrystalized sample,indicating that the corrosion rate of the nanocrystalized sample is smaller.(2)The ultrasonic surface rolling equipment is used to treat YG8 cemented carbide.With the increasing rolled pressure,the grain refinement and hardness increase,and the surface deformation layer becomes thicker.Ultrasonic surface rolling treatment can improve the surface roughness of the sample.The electrochemical corrosion behavior of ultrasonic surface rolled WC-8Co cemented carbide was performed in 3.5% Na Cl solution.It was found that after ultrasonic rolled,the sample impedance spectrum radius increased,the corrosion potential of polarization curve shifted positively,and the corrosion current density decreased.More corrosion products were produced on the sample surface after rolling,and the passivation film was compact.It shows that the corrosion resistance of the specimen is improved after ultrasonic surface rolling treatment.(3)The surface nanocrystallization cemented carbide was used as the substrate material in the TiAlN film,and the microstructure of the film obtained a larger thickness after nanocrystallization.The surface hardness of the films after nanocrystallization is about 24.3%higher than that before nanocrystallization,and the binding force of the films after nanocrystallization is about 35.23% higher than that before surface nanocrystallization.The results of friction and wear curve and wear rate show that the nano-TiAlN films maintain better wear resistance.Meanwhile,the results of electrochemical impedance spectroscopy and polarization curves show that the corrosion resistance of TiAlN films after surface nanocrystallization is better.